The ultimate conversion of monomers in an aqueous polymerization system such as suspension, emulsion or dispersion is often very high: usually in excess of 90 or 95, and often more than 99 percent. However, due to environmental emission and safety standards, it is generally necessary to remove and recover residual, unreacted monomers from the resulting aqueous polymerization system such as a latex composition as well as small amounts of dimers, trimers, oligomers, and non-polymer by-products. While the quantity of dimers and other oligomers is generally very low relative to the amount of residual monomers present in most latices, these oligomers are frequently more objectionable and difficult to remove than the residual monomers. Specifically, larger molecules such as oligomers formed during a variety of suspension, emulsion or dispersion polymerization processes are often odorous and diffuse through the polymer particles of the latices at much slower rates than the residual monomers, and tend to remain trapped within the polymer particles during conventional monomer recovery processes such as evacuation, steam stripping, nitrogen stripping, etc.
While solvent extraction can be used for decreasing the amount of VOCs having relatively high boiling point temperatures to an acceptable level, it requires large quantities of solvent which must be subsequently purified for reuse such as by flash distillation. Moreover, the cost of the extraction and solvent purification equipment, and the energy consumption of the associated processes generally eliminates solvent extraction as a viable method for removing VOCs from latices. Another disadvantage is that significant amounts of solvent remain in the latex and can adversely affect the stability of the latex, cause coagulation or foaming, and require further treatment to remove the solvent.